Apparatus and Method for Conditional Lower Layer Triggered Mobility in Wireless Communication System

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based on and claims priority under 35 U.S.C. § 119(a) of a Korean patent application number 10-2024-0056923, filed on Apr. 29, 2024, in the Korean Intellectual Property Office, and of a Korean patent application number 10-2024-0093322, filed on Jul. 15, 2024, in the Korean Intellectual Property Office, the disclosure of each of which is incorporated by reference herein in its entirety.

The disclosure relates to moving operations of a conditional mobility user equipment (UE) in a wireless communication system. More particularly, the disclosure relates to conditional mobility.

Fifth generation (5G) mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in “Sub 6 gigahertz (GHz)” bands such as 3.5 GHz, but also in “Above 6 GHz” bands referred to as mm Wave including 28 GHz and 39 GHz. In addition, it has been considered to implement sixth generation (6G) mobile communication technologies (referred to as Beyond 5G systems) in terahertz (TH2) bands (for example, 95 GHz to 3 THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies.

At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency

Communications (URLLC), and massive Machine-Type Communications (mMTC), there has been ongoing standardization regarding beamforming and massive multiple-input and multiple-output (MIMO) for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of BandWidth Part (BWP), new channel coding methods such as a Low Density Parity Check (LDPC) code for large amount of data transmission and a polar code for highly reliable transmission of control information, layer 2 (L2) pre-processing, and network slicing for providing a dedicated network specialized to a specific service.

Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as Vehicle-to-everything (V2X) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, New Radio Unlicensed (NR-U) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, NR UE Power Saving, Non-Terrestrial Network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning.

Moreover, there has been ongoing standardization in air interface architecture/protocol regarding technologies such as Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, Integrated Access and Backhaul (IAB) for providing a node for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and Dual Active Protocol Stack (DAPS) handover, and two-step random access for simplifying random access procedures (2-step random access channel (RACH) for NR). There also has been ongoing standardization in system architecture/service regarding a 5G baseline architecture (for example, service based architecture or service based interface) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) for receiving services based on UE positions.

As 5G mobile communication systems are commercialized, connected devices that have been exponentially increasing will be connected to communication networks, and it is accordingly expected that enhanced functions and performances of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research is scheduled in connection with extended Reality (XR) for efficiently supporting Augmented Reality (AR), Virtual Reality (VR), Mixed Reality (MR) and the like, 5G performance improvement and complexity reduction by utilizing Artificial Intelligence (AI) and Machine Learning (ML), AI service support, metaverse service support, and drone communication.

Furthermore, such development of 5G mobile communication systems will serve as a basis for developing not only new waveforms for providing coverage in terahertz bands of 6G mobile communication technologies, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technology using Orbital Angular Momentum (OAM), and Reconfigurable Intelligent Surface (RIS), but also full-duplex technology for increasing frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technology for implementing system optimization by utilizing satellites and Artificial Intelligence (AI) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at levels of complexity exceeding the limit of UE operation capability by utilizing ultra-high-performance communication and computing resources.

With the advance of wireless communication systems as described above, various services can be provided, and accordingly there is a need for ways to effectively provide these services.

The above information is presented as background information only to assist with an understanding of the disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the disclosure.

Aspects of the disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the disclosure is to provide an apparatus and a method for conditional moving so as to eliminate uncertainty in signals provided during lower layer-based inter-cell moving performed by a UE.

Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments.

In accordance with an aspect of the disclosure, a method performed by a user equipment (UE) in a wireless communication system is provided. The method includes receiving, from a base station on a serving cell, configuration information on a conditional lower layers triggered mobility (CLTM), performing a measurement on cells, based on the configuration information, and performing a handover to one cell of the cells, based on a result of the measurement.

In accordance with an aspect of the disclosure, a method performed by a distributed unit (DU) on a serving cell in a wireless communication system is provided. The method includes transmitting, to a central unit (CU), condition information on a conditional lower layers triggered mobility (CLTM), and transmitting, to a user equipment (UE), configuration information including the condition information.

In accordance with an aspect of the disclosure, a user equipment (UE) in a wireless communication system is provided. The UE includes a transceiver, and a controller coupled with the transceiver and configured to receive, from a base station (BS) on a serving cell, configuration information on a conditional lower layers triggered mobility (CLTM), perform a measurement on cells, based on the configuration information, and perform a handover to one cell of the cells, based on a result of the measurement.

In accordance with an aspect of the disclosure, a base station (BS) in a wireless communication system is provided. The BS includes a transceiver, and a controller coupled with the transceiver and configured to transmit, to a central unit (CU), condition information on a conditional lower layers triggered mobility (CLTM), and transmit, to a user equipment (UE), configuration information including the condition information.

According to an embodiment of the disclosure, in case that a specific condition is satisfied when performing lower layer measurement, a UE may perform inter-cell moving even when a signal received from a base station is unstable as the UE moves on its own.

Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the disclosure.

The same reference numerals are used to represent the same elements throughout the drawings.

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the disclosure is provided for illustration purpose only and not for the purpose of limiting the disclosure as defined by the appended claims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces.

In the following description, terms for identifying access nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, and the like are illustratively used for the sake of descriptive convenience. Therefore, the disclosure is not limited by the terms as described below, and other terms referring to subjects having equivalent technical meanings may also be used.

In the following description, a base station is an entity that allocates resources to terminals, and may be at least one of a gNode B, an eNode B, a Node B, a base station (BS), a wireless access unit, a base station controller, and a node on a network. A terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing a communication function. In the disclosure, a “downlink (DL)” refers to a radio link via which a base station transmits a signal to a terminal, and an “uplink (UL)” refers to a radio link via which a terminal transmits a signal to a base station. Furthermore, in the following description, LTE or LTE-Advanced (LTE-A) systems may be described by way of example, but the embodiments of the disclosure may also be applied to other communication systems having similar technical backgrounds or channel types. Examples of such communication systems may include 5th generation mobile communication technologies (5G, new radio, and NR) developed beyond LTE-A, and in the following description, the “5G” may be the concept that covers the exiting LTE, LTE-A, and other similar services. In addition, based on determinations by those skilled in the art, the disclosure may be applied to other communication systems through some modifications without significantly departing from the scope of the disclosure. Herein, it will be understood that each block of the flowchart illustrations, and combinations of blocks in the flowchart illustrations, can be implemented by computer program instructions.

These computer program instructions can be provided to a processor of a general-purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart block or blocks. These computer program instructions may also be stored in a computer usable or computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer usable or computer-readable memory produce an article of manufacture including instruction means that implement the function specified in the flowchart block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks.

Furthermore, each block in the flowchart illustrations may represent a module, segment, or portion of code, which includes one or more executable instructions for implementing the specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. As used in embodiments of the disclosure, the term “unit” refers to a software element or a hardware element, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC), and the “unit” may perform certain functions. However, the “unit” does not always have a meaning limited to software or hardware. The “unit” may be constructed either to be stored in an addressable storage medium or to execute one or more processors. Therefore, the “unit” includes, for example, software elements, object-oriented software elements, class elements or task elements, processes, functions, properties, procedures, sub-routines, segments of a program code, drivers, firmware, micro-codes, circuits, data, database, data structures, tables, arrays, and parameters. The elements and functions provided by the “unit” may be either combined into a smaller number of elements, or a “unit”, or divided into a larger number of elements, or a “unit”. Moreover, the elements and “units” may be implemented to reproduce one or more central processing units (CPUs) within a device or a security multimedia card. Furthermore, the “unit” in embodiments may include one or more processors.

In the following description of the disclosure, terms and names defined in 5GS and NR standards, which are the standards specified by the 3rd generation partnership project (3GPP) group among the existing communication standards, will be used for the sake of descriptive convenience. However, the disclosure is not limited by these terms and names, and may be applied in the same way to systems that conform other standards. For example, the disclosure may be applied to the 3GPP 5GS/NR (5th generation mobile communication standards).

It should be appreciated that the blocks in each flowchart and combinations of the flowcharts may be performed by one or more computer programs which include instructions. The entirety of the one or more computer programs may be stored in a single memory device or the one or more computer programs may be divided with different portions stored in different multiple memory devices.

Any of the functions or operations described herein can be processed by one processor or a combination of processors. The one processor or the combination of processors is circuitry performing processing and includes circuitry like an application processor (AP, e.g. a central processing unit (CPU)), a communication processor (CP, e.g., a modem), a graphics processing unit (GPU), a neural processing unit (NPU) (e.g., an artificial intelligence (AI) chip), a wireless fidelity (Wi-Fi) chip, a Bluetooth® chip, a global positioning system (GPS) chip, a near field communication (NFC) chip, connectivity chips, a sensor controller, a touch controller, a finger-print sensor controller, a display driver integrated circuit (IC), an audio CODEC chip, a universal serial bus (USB) controller, a camera controller, an image processing IC, a microprocessor unit (MPU), a system on chip (SoC), an IC, or the like.

illustrates a structure of a wireless communication system (e.g., LTE system) according to an embodiment of the disclosure.

Referring to, a radio access network of an LTE system may include next-generation base stations (evolved node Bs, hereinafter ENBs, node Bs, or base stations),,, and, a mobility management entity (MME), and a serving gateway (S-GW). A user equipment (hereinafter UE or terminal)may access an external network through the ENBstoand the S-GW.

In, the ENBstomay correspond to a conventional node B in a UMTS system. The ENBs may be connected to the UEthrough a radio channel, and perform more complicated roles than the conventional node Bs. In the LTE system, since all user traffic including real-time services, such as voice over IP (VoIP) via the Internet protocol, may be serviced through a shared channel. Thus, a device that collects state information, such as buffer states, available transmit power states, and channel states of UEs, and performs scheduling accordingly is required, and the ENBstomay serve as the device. In general, one ENB may control multiple cells. For example, in order to implement a transfer rate of 100 Mbps, the LTE system may use orthogonal frequency division multiplexing (OFDM) as a radio access technology in a bandwidth of, for example, 20 MHz. Furthermore, the LTE system may employ an adaptive modulation & coding (AMC) scheme for determining a modulation scheme and a channel coding rate according to a channel state of a UE. The S-GWis a device that provides a data bearer, and may generate or remove a data bearer under the control of the MME. The MME is a device responsible for various control functions as well as a mobility management function for a UE, and may be connected to multiple base stations.

illustrates a radio protocol structure of a wireless communication system (e.g., LTE system) according to an embodiment of the disclosure.

Referring to, a radio protocol of an LTE system may include a packet data convergence protocol (PDCP)or, a radio link control (RLC)or, and a medium access control (MAC)oron each of UE and ENB sides. The PDCP may serve to perform operations such as IP header compression/reconstruction. The main functions of the PDCP may be summarized as follows.

The radio link control (RLC)ormay reconfigure a PDCP protocol data unit (PDU) into an appropriate size to perform an ARQ operation. The main functions of the RLC may be summarized as follows.

The MACormay be connected to several RLC layer devices configured in a single terminal, and multiplex RLC PDUs into a MAC PDU and demultiplex a MAC PDU into RLC PDUs. The main functions of the MAC are summarized as follows.

A physical layerormay perform operations of channel-coding and modulating upper layer data, thereby obtaining OFDM symbols, and delivering the same through a radio channel, or demodulating OFDM symbols received through the radio channel, channel-decoding the same, and delivering the same to the upper layer.

illustrates a structure of a wireless mobile communication system according to an embodiment of the disclosure.

Referring to, a radio access network of a wireless mobile communication system (hereinafter NR or 5G) may include a new radio node B (hereinafter NR gNB or NR base station), and a new radio core network (NR CN). A new radio user equipment (NR UE or NR terminal)may access an external network via the NR gNBand the NR CN.

In, the NR gNBmay correspond to an evolved node B (eNB) of a conventional LTE system. The NR gNB may be connected to the NR UEthrough a radio channel and provide outstanding services as compared to a conventional node B. In the next-generation mobile communication system, since all user traffic may be serviced through a shared channel. Thus, a device that collects state information, such as buffer states, available transmit power states, and channel states of UEs, and performs scheduling accordingly is required, and the NR gNBmay serve as the device. In general, one NR gNB may control multiple cells. In order to implement ultrahigh-speed data transfer beyond the current LTE, the next-generation mobile communication system may provide a wider bandwidth than the existing maximum bandwidth. in addition, the next-generation mobile communication system may employ an orthogonal frequency division multiplexing (OFDM) as a radio access technology, and may additionally integrate a beamforming technology therewith. Furthermore, the next-generation mobile communication system may employ an adaptive modulation & coding (AMC) scheme for determining a modulation scheme and a channel coding rate according to a channel state of a UE. The NR CNmay perform functions such as mobility support, bearer configuration, and quality of service (QOS) configuration. The NR CN is a device responsible for various control functions as well as a mobility management function for a UE, and may be connected to multiple base stations. In addition, the next-generation mobile communication system may interwork with the existing LTE system, and the NR CN may be connected to an MMEvia a network interface. The MME may be connected to an eNBthat is an existing base station.

illustrates a radio protocol structure of a wireless mobile communication system according to an embodiment of the disclosure.

Referring to, a radio protocol of a wireless mobile communication system may include an NR service data adaptation protocol (SDAP)or, an NR PDCPor, an NR RLCor, an NR MACor, and an NR physical (PHY)oron each of UE and NR base station sides.

The main functions of the NR SDAPormay include some of functions below.

With regard to the SDAP layer device, whether to use the header of the SDAP layer device or whether to use functions of the SDAP layer device may be configured for the UE through a radio resource control (RRC) message according to PDCP layer devices or according to bearers or according to logical channels. If an SDAP header is configured, the non-access stratum (NAS) quality of service (QOS) reflection configuration 1-bit indicator (NASreflective QoS) of the SDAP header and the access stratum (AS) QoS reflection configuration1-bit indicator (AS reflective QoS) may indicate, to the UE, that the UE can update or reconfigure mapping information regarding the QoS flow and data bearer of the uplink and downlink. The SDAP header may include QoS flow ID information indicating the QoS. The QoS information may be used as data processing priority, scheduling information, etc. for smoothly supporting services.

The main functions of the NR PDCPormay include some of functions below.

The above-mentioned reordering of the NR PDCP device may refer to a function of reordering PDCP PDU received from a lower layer in an order based on PDCP sequence numbers (SNs). The reordering of the NR PDCP device may include a function of transferring data to an upper layer according to a rearranged order, may include a function of directly transferring data without considering order, may include a function of rearranging order to record lost PDCP PDUs, may include a function of reporting the state of lost PDCP PDUs to a transmission side, and may include a function of requesting retransmission of lost PDCP PDUs.

The main functions of the NR RLCormay include some of functions below.

The above-mentioned in-sequence delivery of the NR RLC device refers to a function of delivering RLC SDUs, received from the lower layer, to the upper layer in sequence. If one original RLC SDU is divided into several RLC SDUs and the RLC SDUs are received, the in-sequence delivery function of the NR RLC device may include a function of reassembling the several RLC SDUs and transferring the reassembled RLC SDUs.